Piezoelectric pump



Sept. 29, 1964 c. L. sTEc PIEZOELEC'I'RIC PUMP 2 Sheets-Sheet 1 Filed Aug. 17, 1962 INVENTOR cHA L. STEC' ATTORNEYS Sept. 29, 1964 c. STEC PIEZOELECTRIC PUMP 2 Sheets-Sheet 2 Filed Aug. 17. 1962 0 O o OR 20 w. h 2 n m I F 6 v 4 6 9 8 a W o W w w w x r 4 w 0 9 t w Y 1 a 0 C W.- 3 8 M 8 N A 8 N o U G (l on 8 IQ I 8 E o Y R V F m F a .W. m 8 8 0 9 O 5 o L. L. M 1 4 .0 o fi v .rzuzuudJmwa m 4 =m o CHARLES L. srgc FIG. 4.

ATTORNEY United States Patent Ofi ice 3,150,592 Patented Sept. 29, 1964 3,150,592 PIEZOELECTRIC PUMP Charles L. Stec, 2725 N. Nelson St., Arlington 7, Va. Filed Aug. 17, 1962, Ser. No. 219,361 24 Claims. (Cl. 103-1) (Granted under Title 35, US. Code (1952), see. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

This invention relates to a fluid pump, and more particularly to a pump that utilizes the dimensional change characteristics of piezoelectric materials as a volume changing device.

This application is a continuatiou-in-part of application Serial No. 25,178, filed April 27, 1960, now abandoned.

The majority of the prior art pumps rely for their operation upon a plurality of mechanically moving elements that, by their nature, create a great deal of noise and are therefore objectionable on a submarine or other ships where it is desired to maintain as low a noise level as possible to prevent detection. Accordingly, there has been a long felt need for a pump that is substantially free of mechanically moving parts and is silent in operation. Pursuant to a solution of the aforementioned noise problem, the instant silent pump has been invented, and utilizes the properties of certain piezoelectric materials to provide the pumping, or volume changing, element of the pump.

As is well known in the art, certain piezoelectric materials, such as for example quartz crystals, rochelle salt, barium titanate and compounds of barium titanate have piezoelectric properties. Suitable barium titanate compounds are commercially available and are barium titanate with lead or calcium additives in a range of plus or minus 3%, or lead zirconate additives. Many of these materials are adapted to be formed in various shapes and sizes and are adapted to be formed into configurations whose opposite faces can be or are polarized with respect to one another. When a piezoelectric material, such as barium titanate, is so polarized and has a voltage applied to its faces, the material will change shape and/or dimension. It is this latter phenomenon that is taken advantage of in the instant invention. In the instant invention a varying pumping voltage is applied which causes the material to expand and contract with respect to its normal condition or dimensions when no voltage is applied.

As indicated above, one of the advantages of the instant pump is that it is silent in operation, thereby making it particularly valuable for use aboard naval vessels where noise reduction is an ever present problem. In addition to noise reduction, the instant pump reduces maintenance problems arising from wear and/ or breakage such as is present in the moving parts of conventional prior art pumps.

It is also pointed out that by using moldable barium titanate or other piezoelectric materials in making the pumping element, or elements, of the instant invention, it is easy to provide pumps of various sizes and configurations. It is accordingly an object of this invention to provide a pump adapted to overcome the disadvantages of the prior art pumping devices.

Another object of this invention is to provide a pump that is free of mechanically moving parts such as are present, for example, in reciprocating piston pumps and rotary pumps.

Still another object of this invention is to provide a pump that is noiseless in operation.

An added object of this invention is to provide a pump that utilizes the characteristics of piezoelectric materials to provide a pumping action.

A further object of this invention is to provide a pump that is free of the mechanical friction losses inherent to prior pumps.

Still a further object is to provide a pump that can readily be produced in various different sizes and shapes.

An additional object of this invention is to provide a pump that can be readily produced and maintained with relatively little expense and by relatively unskilled labor.

Other objects and many of the attendant advantages of this invention will be readily appreciated from a consideration of the following detailed description when taken in connection with the accompanying drawings by way of example only, wherein:

FIG. 1 is a view, partially in section, and partially broken away, of one embodiment of the instant inventive p p;

FIG. 2 is a sectional view of another embodiment of the instant invention;

FIG. 3 is a curve indicating operational characteristics of a pump similar to that shown in FIG. 1, with the abscissae representing root mean square A.C. voltages of 20 cycles per second on a linearly increasing magnitude from zero, and the ordinates representing capillary displacement of output liquid on a linearly increasing magnitude from zero; and

FIG. 4 is a curve showing the volumetric relation as ordinates to AC. frequency of the energizing source as abscissae, the energizing AC. voltage being constant at 500 volts, for a pump in accordance with the invention when pumping oil, and

FIG. 5 is a central cross-sectional view of a modified form of piezoelectric pump.

Referring now to the drawings wherein like reference characters designate like or corresponding parts throughout the several views, there is shown in FIG. 1 a pump assembly 10 embodying the invention. The assembly 10 includes a pump 12 connected by an inlet pipe line 14, having a valve 16 therein, to a fluid reservoir 18 having a quantity of fluid 20 therein.

In accordance with the embodiment of the invention shown in FIG. 1, the pump 12 includes a hollow outer casing or body 22 made of steel or some other rigid material, and having a spherical configuration, for example, being formed of tWo flanged hemispheres 24 and 26 connected together by a plurality of bolts 28.

A hollow sphere or body 30 is mounted or nested within the inner space or chamber of the sphere 22 and is held in spaced relation with the interior surface of the sphere 22 by a plurality of spacer discs 32 to form a fluid holding or pumping chamber 33. The spacers may be made of any suitable material. Examples of such materials are polyethylene and hard rubber. A minimum number of spacers should be used consistent with maintaining the spheres spaced. Preferably the spheres 22 and 30 are concentric so that the pump chamber 33 has a uniform thickness. Such uniform thickness can obviously be obtained with the inner surface of body 22 and the outer surface of body 30 being surfaces of revolution of geometrically similar curved lines terminating on the axis of revolution.

The sphere 30 is formed of a piezoelectric material such as barium titanate. Barium titanate compounds are used in the preferred embodiment of the invention, since they have the greatest piezoelectric displacement characteristics of materials presently known, and are readily moldable to various shapes. It is however emphasized that the practice of the invention need not be limited to barium titanate or its compounds, but that any suitable type of piezoelectric material can be utilized.

The inner and outer surfaces or faces of the inner sphere 30 are coated with an electrode 34 and 46, respectively; the inner electrode 34 having an electrical lead 38 electrically connected thereto and extending through the walls of the spheres 30 and 22 to one pole of a reversing switch mechanism 40. The outer electrode 36 has a lead 42 which is electrically connected thereto and extends through the outer sphere 22 to the other pole of the reversing switch 40. The reversing switch 40 may be either electronically operated or driven by a motor or the like 44 and is connected to a suitable energizing source of DC. voltage.

At the points where leads 38 and 42 pass through the respective spheres 30 and 22, said leads are surrounded .by fluid tight grommets 46 fitted into holes formed in the spheres 30 and 22 in such a manner as to prevent passage of fluid through the wall of either sphere.

Utilizing the well known characteristics of piezoelectric materials, and more particularly barium titanate, or its compounds, the sphere 30 is so formed that the inner and outer surfaces thereof are oppositely polarized. For example, the inner surface may be polarized positive and the outer surface negative. The polarization process does not form a part of the instant invention, and can be achieved by various means. However, and by way of example, one polarization process includes first placing a piezo-electric specimen in a holder and immersing the specimen into an oil bath. A silicone oil has been found particularly satisfactory because of its range of temperature and voltage flash point.

The oil is then heated above the Curie point of the piezoelectric specimen, which is usually up to about 130 C. A DC. voltage is then applied to the specimen, after which said specimen is allowed to cool down through the Curie point and the voltage is held until the temperature of the specimen has returned to about 50 C. The amount of voltage applied is determined by the thickness of the sample. It has been found that 7.5 kv. per centimeter is the optimum voltage to be used.

The reason for polarizing hot is that a smaller voltage can be used, and there is less chance for arcing across the edges of the specimen. In the cold method of polarization, the amount of voltage used is approximately 80 kv. per inch.

The materials resulting from the above referred to processes are known as electrically polarized piezoelectric materials.

When a DC. voltage is applied to the surfaces of sphere 30, through the switch 40 and the leads 38 and 42 of the electrodes 34 and 36, and is periodically reversed, alternate radial expansion and contraction of the sphere 30 occurs, while the outer sphere 22 remains fixed in size.

By virtue of the alternate expansion and contraction of the sphere 30, the pump space or chamber 33 between the inner and outer spheres contracts and expands becoming alternately larger than and smaller than its size when no such D.C. voltage is applied.

The outer sphere 22 is connected to the pipe line 14 by an inlet check valve 47 connected to the lower side thereof. The valve 47 has a fluid passageway extending therethrough in communication with the pump space or chamber 33 between the inner sphere 3t) and the outer sphere 22. The valve 47 only allows inward flow of fluid into the space 33. At a diametrically opposed point on the sphere 22 there is connected an outlet check valve 48 through which fluid is allowed to pass outwardly of the space between the two spheres, but is not allowed to return thereinto. The outlet check valve 48 may in turn be connected to any sort of fluid conduit 49, which for purposes of illustration may be designated as a capillary tube.

When the inner sphere 30 is caused to contract by the application of a suitable voltage to its electrodes, fluid is sucked into the pump space 33 between the two spheres through the check valve 47. When the charge on the respective electrodes 34 and 36 of the sphere 39 is reversed or at least quantitatively varied in an opposite direction, the operation is reversed. The sphere expands, the check valve 47 closes, and fluid is forced out of the chamber 33 through the check valve 48. As the voltage charges on the electrodes 34 and 35 are cyclically reversed, through the action of the reversing switch 40, the pumping action continues at the frequency of the reversing switch. It is pointed out that the change in volume on the part of the sphere 30 is governed by the frequency and magnitude of the voltages applied to the electrodes 34 and 36.

Instead of a reversing DC. voltage, an AC. voltage may be connected to the conductors 38 and 42 to expand and contract the sphere 30.

Referring to FIG. 2 wherein is shown another embodiment of the invention, it is emphasized that this embodiment is, for reasons hereinafter set forth, capable of about double the pumping capacity of the embodiment shown in FIG. 1.

The embodiment of the invention shown in FIG. 2 comprises a pump 12' that includes a rigid steel outer casing body or sphere 22' which comprises a pair of hemispheres 24' and 26 bolted together by a plurality of bolts 28'. The sphere 22' is hollow so as to provide an internal space that receives the pumping elements.

The pump 12 has a first, or outermost, pumping body or sphere 50 of piezoelectric material, such as barium titanate, concentrically mounted within the sphere 22' and held in spaced relation therefrom by a plurality of disc-like spacer members 51 similar to spacers 32 of FIG. 1. For ease of fabrication, the sphere 50 is made up of two hemispheres, the abutting edges of which are cemented together by any suitable cement such as an epoxy resin cement, or for that matter any cement that is insoluble in the fluid being pumped. The entire inner surface or face of the sphere 50 is coated with an electrode 52 and the entire outer surface or face is coated with an electrode 54. The sphere 50 is hollow and provides a chamber for receiving a second pumping body or sphere 56 of this same polarized material as sphere 50. The sphere 50 may be considered to be a casing for sphere 56. All of the spheres are fluid-tight.

The second sphere 56 is mounted concentrically within sphere 50, and is spaced therefrom to provide a pump chamber therebetween. The sphere 56 is held in spaced relation relative to the sphere 50 by a plurality of spacers '58 similar to the spacers 51. The inner and outer surfaces or faces of the sphere 56 are fully coated with electrodes 60 and 62 respectively.

The spheres 50 and 56 are so polarized that the inner surfaces of the respective spheres are polarized alike, that is, both inner surfaces may for example be positive while the outer surface of each sphere is polarized negative.

The inner electrode 60 of the inner sphere 56 is electrically connected by means of electrical leads 64 and 66 to the outer electrode 54 of the outer sphere 50, and to one terminal of a reversing switch 40', while the outer electrode 62 of the inner sphere 50 is connected to the inner electrode 52 of the outer sphere 56 which connection is in turn connected, by a lead 68, to the other terminal of the reversing switch 40'. Such connection avoids a voltage gradient across the pump space between the spheres, thereby eliminating the danger of arcing in said space.

The switch 40 is in turn connected to a source of DC. voltage. The switch 40' in FIG. 2 is provided with a switch reversing motor 44', and in all ways the switch 40' is identical to the switch 40 shown in FIG. 1.

It is emphasized that, by virtue of the manner of connection between the electrodes of the outer and inner spheres 5t and 56, when a positive DC. voltage is applied to the inner electrode 60 of the inner sphere 56 a like positive voltage is applied to the outer electrode 54 of the outer sphere 5b, and at the same time a negative voltage is applied to both the outer electrode 62 .timeters in 60 seconds.

of the inner sphere 56 and the inner electrode 52 of the outer sphere 50. Accordingly, one sphere is, for example, caused to expand and the other to contract in opposition, thereby providing about double the pumping capacity, for the same sizes, voltage, and frequency, as is possible with the construction shown in FIG. 1.

In order to admit fluid into the pump space between the outer and inner spheres 5t and 56, a tubular fitting 70 is extended through, and aflixed to, the outer casing 22' and extends into and through the wall of the outer sphere 50 providing a fluid passageway into the space between the spheres. The fitting 70 may then in turn be connected to a fluid reservoir, such as 18 shown in FIG. 1, and includes a check valve such as valve 47 (FIG. 1). Fluid passes out of the pump space between the spheres 50 and 56 through a tubular fitting 72 that extends through the outer sphere 50 and the outer casing 22, said fitting 72 in turn being connected to a check valve, such as the valve 48 shown in FIG. 1, so as to allow fiuid to pass only outwardly of the pump 12.

The initial polarization of the respective surfaces of the two spheres 50 and 56, the manner of the electrical connections between the electrodes on the respective surfaces of said spheres, and the reversing switch 40 of the embodiment of the invention shown in FIG. 2 causes this embodiment to operate in such a manner as to cause simultaneous expansion of one sphere and contraction of the other.

While a mechanical switching arrangement, such as 40, has been shown as being used in the instant invention, the invention is not limited to such mechanical apparatus, since it is within the scope of the invention to utilize an A.C. energizing source or an electronic switching gear or any other suitable reversing means. If an A.C. energizing source is used, it may be an electronic oscillator or a power line of an A.C. system or any other form. The use of an electronic switching arrangement or an A.C. energizing source in conjunction with the embodiment shown in FIGS. 1 and 2, respectively, results in a pump that is completely free of mechanically moving parts and is essentially completely noiseless, thus rendering the pump especially useful aboard ships where maintenance of the noise level at a minimum is quite imperative.

By way of example only, and in no sense to be considered limiting, an operating form of the embodiment shown in FIG. 2 has been manufactured, wherein the outer sphere 50 had an outside diameter of 5 inches and a wall thickness of .200 inches. The inner sphere 56 was spaced .025 inches from the inner surface of the outer sphere 50, had an outside diameter of 4.55 inches, and a thickness of .200 inches.

Using an output capillary tube with the discharge fitting 72 in the structure described in the preceding paragraph, having an inside diameter of .061 inches, and with a DC. voltage of 200 volts alternatively applied to the opposite surfaces of the respective spheres 50 and 56, at 1820 pulses per minute, the pumped oil in the capillary tube rose a distance of approximately 41 cen- Using a capillary tube having a diameter of .126 inches and 400 DC. volts at 510 pulses per minute, the oil rose approximately 30 centimeters in 60 seconds.

The amount of liquid pumped per unit time is a function of the voltage applied across the faces of each sphere, the number of pulses per unit time, and the material characteristics of the spheres 50 and 56.

The curves of FIGS. 3 and 4 were obtained with a pump with two concentric piezoelectric spheres. The inner sphere of barium titanate with lead additive had an outer diameter of 4.44 inches and a wall thickness of .25 inch. A similar concentric outer sphere had an inside diameter 4.5 inches. The capillary tube associated therewith on the output side was a polystyrene tube of .1 inch inside diameter.

FIG. 3 illustrates operating characteristics of the embodiment when an A.C. source of 20 cycles per second was utilized as the driving source. It may be observed that as the R.M.S. voltage increased, the volume output increased linearly in direct proportion to the magnitude of the voltage.

In general, for the particular piezoelectric pump tested, a greater volume output is obtained at relatively lower frequencies, other conditions being equal. The relationship is represented in FIG. 4 for A.C. energizat-ion. It does not appear to be linear with frequency. In FIG. 4 the solid line is for a pump when the outer sphere only was energized; and the broken line when both spheres V were in series. The volumetric output is much higher, relatively, at the lower frequencies than at the relatively higher frequencies of, say 150 c.p.s. and above. In FIG. 4, the output approaches an asymptotic value as frequency increases with constant Voltage. This is attributed to the inability of the pumped liquid to follow the volume displacement because of internal liquid friction. However, the shape of the curve depends largely on such factors as fluid viscosity, size of pumping elements, and characteristics of the piezoelectric material of the pump; and a corresponding curve for a different pump may be quite different from that shown in FIG. 4.

It has also been found that the viscosity of the liquid pumped is a parameter in the operation of the pump; and in ranges of from 10* to 1 poise, a test of a pump pumping oils showed viscosity to have a small eifect on the output of the pump. Tests have also shown that the pump will pump liquid against a back pressure of over 1500 pounds per square inch.

The outline shapes at the pump chamber of the pump members of the pump may take forms other than spheres. Those formed by nested surfaces of revolution are preferred.

FIG. 5 shows a specific piezoelectric pump of a cylindrical form generally corresponding to a rectangle rotated on its long side as an axis. The pump comprises an outer pump member in the form of a hollow cylindrical tube and two polystyrene end plates 82 and 84 clamping the tube 80 therebetween. Circular gaskets 86 are interposed at the ends of the tube to insure liquidtight joints. The gaskets are thin and of low compressibility to insure that pumping volume is not adversely affected. The tube 80 is made of an electrically polarized piezoelectric material provided with inner and outer surface-electrodes across which a suitable driving voltage may be connected. The end plates are mechanically tied together with tie-rods 88 in a hexagonal arrangement.

The upper end plate 82 is provided with a discharge or outlet 90 provided with an outlet check valve; and the lower end plate 84 is provided with an inlet 92 provided with an inlet check valve.

Also clamped between the end plates is a cylindrical inner pump member 94 and spacers 96, similar to spacers 51, which aid in keeping the inner pump member centered in the outer pump member so as to provide a pump chamber 9%. In the specific embodiment, the pump-member 94 is in the form of a solid cylinder of stainless steel.

The inlet 92 and outlet 90 are shown in FIG. 5 as located centrally of the pump-chamber; but either or both may be at the annular edge of the chamber 98.

In the specific embodiment described, the tube 80 of the outer pump member had a length of 2 inches, an outside diameter of 2 inches and a wall thickness of .125 inch. The inner pump member had an outer diameter of 1.50 inches. It was radially spaced .25 inch from the outer pumping member and axially spaced about inch at both ends.

What is claimed is:

1. A pump comprising a pair of concentric bodies each of said bodies having a pumping surface, said bodies being spaced to provide a pump chamber therebetween, a first of said bodies having piezoelectric characteristics causing an expansion and contnaction in all directions normal to said pumping surface, fluid inlet means to and fluid outlet means from said chamber, and one-way valve means controlling said inlet means and outlet means, said first body having separated electricity-conducting surface portions adapted to having a pumping voltage applied thereto, and means electrically connected to said conducting portions for applying a varying voltage across said conducting portions for alternately and repeatedly increasing and decreasing the volume of said chamber.

2. A pump as defined in claim 1 wherein the last said means comprises a pulsed D.C. voltage source.

3. A pump as defined in claim 1 wherein last said means comprises an AC. voltage source.

4. A pump as defined in claim 1 wherein said first body is a material comprising mostly barium titanate.

5. A relatively silent pump comprising a pair of concentric bodies, said bodies being spaced to provide a pump chamber therebetween a pair of end elements engaging said bodies closing said pump chamber, each of said bodies having radial mode piezoelectric characteristics, a fluid inlet means to and a fluid outlet means from said chamber, and one-Way valve means controlling said inlet means and said outlet means, each of said bodies having an electrode means on its inner and outer surfaces, and means electrically connected to said electrode means for applying a varying voltage to said bodies for alternately and repeatedly increasing and decreasing the volume of said chamher.

6. A pump as defined in claim 5 wherein said bodies are geometrically similar.

7. A pump as defined in claim 5 wherein the last said means comprises parallel connections to the electrode means on the inner surface of the outer of said bodies and to the electrode means on the outer surface of the inner of said bodies. 7

8. A pump comprising a plurality of concentric spaced bodies, a first and second of said bodies being of electrically-polarized radial mode piezoelectric material, a third of said bodies being of a different material, said third bodies enclosing said first and said second bodies, said spaced bodies having a thin pump chamber bounded by a surface of each of said first and second bodies, a pair of end elements engaging said bodies closing said pump chamber, one-way fluid inlet means to and fluid outlet means from said pump chamber, and means to apply a varying voltage to said first and second bodies to cause said chamber alternately to expand and contract.

9. A pump as defined in claim 8 wherein said third body is rigid and non-piezoelectric.

10. A pump comprising, a fluid-tight casing having a closed chamber formed therewithin, an electrically polarized piezoelectric means within said closed chamber forming a thin fluid pumping chamber, means for applying and varying an electric charge to opposite faces of electrically polarized piezoelectric means to cause a dimension of the latter to expand and contract radially for varying the volume of said pumping chamber, inlet valve means connected to said pumping chamber for only admitting fluid into said pumping chamber and outlet valve means connected to said pumping chamber for only allowing fluid to escape from said pumping chamber, whereby upon variation of the charge on the opposite faces of said electrically polarized piezoelectric means fluid will be alternately introduced into and ejected from said pumping chamber.

11. A pump as set forth in claim 10 wherein said fluid tight casing is non-piezoelectric and is in the form of a concentric sphere mounted within said casing and spaced from the inner wall thereof.

12. A pump as set forth in claim 10 wherein said casing is piezoelectric, and said casing and said piezoelectric means are spheres.

13. A pump comprising a pair of concentric bodies, a first of said bodies being non-piezoelectric and rigid and the second being an electrically-polarized radial mode piezoelectric body in spaced relation to said first body to form a pump chamber, said piezoelectric body having opposite faces that are oppositely polarized, electrodes on said faces, a fluid inlet to and a fluid outlet from said pump chamber, said fluid inlet having means therein to allow flow of fluid only into said pump chamber, and said outlet having means therein to allow only outward flow from said pump chamber, and means connected to the electrodes for applying a varying electrical charge to said faces to cause said piezoelectric body to radially expand and contract to vary the volume of said pump chamber, whereby fluid is alternately drawn into said space and ejected therefrom.

14. A pump as set forth in claim 13 wherein said bodies are concentric spheres.

15. A pump as set forth in claim 13 wherein said bodies are cylinders.

16. A pump comprising a first hollow piezoelectric member, said first member having a fluid inlet and a fluid outlet formed therein, valves in said inlet and said outlet permitting fluid to flow respectively only into the interior of the first piezoelectric member and only outwardly of said first piezoelectric member, a second piezoelectric member mounted within said first piezoelectric member and having the exterior surface thereof in spaced relation with the interior of said first piezoelectric member to form a fluid holding chamber, the outer surface of said second piezoelectric member and the inner surface of said first piezoelectric member being electrically connected together in parallel, and the inner surface of said second piezoelectric members and the outer surface of said first piezoelectric member being electrically connected together in parallel; and means for applying a varying electrical charge to the respective pairs of connected together surfaces of said first and second piezoelectric members so as to cause radial expansion of one piezoelectric member .and radial contraction of the other to vary the capacity of the fluid holding chamber therebetween.

17. A pump as set forth in claim 16, wherein each of said piezoelectric members is in the form of a hollow sphere.

18. A pump comprising a fluid-tight casing having an interior surface defining a chamber therewithin, hollow electro-strictive means within said chamber for varying the volume of said chamber, said electro-strictive means having opposite faces, means for applying and varying a charge applied to said opposite faces of said electrostrictive means to cause the latter to expand and contract for varying the volume of said chamber, inlet valve means connected to said chamber for only admitting fluid into said chamber and outlet valve means connected to said chamber for only allowing fluid to escape from said chamber, whereby upon variation of the charge on the opposite faces of said electro-strictive member fluid will be alternately introduced into and ejected from said chamber, said fluid tight casing is in the form of a hollow sphere and said electro-strictive means is in the form of a concentric sphere mounted within said enclosure and spaced from the inner wall of said enclosure.

19. A pump as set forth in claim 18, wherein said electro-strictive sphere is formed of barium titanate.

20. A pump comprising, a plurality of spaced nested members comprising a first hollow electro-strictive member, said first electro-strictive member having a fluid inlet and a fluid outlet formed therein, valves in said inlet and said outlet permitting fluid to flow respectively only into the interior of the first electro-strictive member and only outwardly of said first electro-strictive member, a second electro-strictive member mounted within said first electrostrictive member and having the exterior surface thereof in spaced relation with the interior surface of said first electro-strictive member to form a fluid holding chamber,

said surfaces comprising electrode means, the exterior surface of said second electro-strictive member and the inner surface of said first electro-strictive member being electrically connected together in parallel, and the interior surface of said second electro-strictive member and the outer surface of said first electro-strictive member being electrically connected together in parallel, said first and second electrostrictive members being so fabricated as to provide the inner surface of each of said electrostrictive members with polarization opposite to that of said outer surfaces; and means for applying a varying electrical charge to the electrodes if the respective pairs of connected together surfaces of said first and second electrostrictive members so as to cause expansion of one electrostrictive member and contraction of the other to vary the capacity of the fluid holding chamber therebetween, whereby fluid is adapted to be pumped into said chamber through said fluid inlet and out of said chamber through said fluid outlet.

21. A pump as set forth in claim 20, wherein each of said electro-strictive members is in the form of a hollow sphere.

References Cited in the file of this patent UNITED STATES PATENTS 2,086,891 Bachmann et al. July 13, 1937 2,317,166 Abrams Apr. 20, 1943 2,565,158 Williams Aug. 21, 1951 2,928,409 Johnson et al. Mar. 15, 1960 2,939,970 Dranetz et al. June 7, 1960 

1. A PUMP COMPRISING A PAIR OF CONCENTRIC BODIES EACH OF SAID BODIES HAVING A PUMPING SURFACE, SAID BODIES BEING SPACED TO PROVIDE A PUMP CHAMBER THEREBETWEEN, A FIRST OF SAID BODIES HAVING PIEZOELECTRIC CHARACTERISTICS CAUSING AN EXPANSION AND CONTRACTION IN ALL DIRECTIONS NORMAL TO SAID PUMPING SURFACE, FLUID INLET MEANS TO AND FLUID OUTLET MEANS FROM SAID CHAMBER, AND ONE-WAY VALVE MEANS CONTROLLING SAID INLET MEANS AND OUTLET MEANS, SAID FIRST BODY HAVING SEPARATED ELECTRICITY-CONDUCTING SURFACE PORTIONS ADAPTED TO HAVING A PUMPING VOLTAGE APPLIED THERETO, AND MEANS ELECTRICALLY CONNECTED TO SAID CONDUCTING PORTIONS FOR APPLYING A VARYING VOLTAGE ACROSS SAID CONDUCTING PORTIONS FOR ALTERNATELY AND REPEATEDLY INCREASING AND DECREASING THE VOLUME OF SAID CHAMBER. 